Monotremes

Definition

Monotremes are a unique group of egg-laying mammals found mainly in Australia and New Guinea. They include the platypus and echidnas, which exhibit both reptilian and mammalian traits.

5 Must Know Facts For Your Next Test

1. Monotremes are one of the three main groups of mammals, alongside marsupials and placental mammals.
2. They lay eggs instead of giving birth to live young, a trait rare among mammals.
3. Monotremes possess mammary glands but lack nipples; milk is secreted through openings in the skin.
4. The platypus has a bill that can detect electrical signals from prey underwater, an adaptation not seen in other mammals.
5. Monotreme reproductive anatomy includes a cloaca, a single opening for excretion and reproduction, similar to reptiles.

Review Questions

• What distinguishes monotremes from other groups of mammals?
• Which two animals are classified as monotremes?
• How do monotremes feed their young if they lack nipples?

Related terms

Marsupials: Mammals that give birth to underdeveloped young which typically continue to develop in a pouch on the mother's belly.

Placental Mammals: Mammals that nourish their developing embryos via a placenta before giving birth to live young.

Cloaca:

A common cavity at the end of the digestive tract for the release of both excretory and genital products in some animals including monotremes.